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Re: 465 bad rise time
You are looking at the waveform with a scope probe that presents a 10 meg ohm load to the pulse generator. What you need to do is use a 50 ohm cable to go from the generator to the scope input and include a 50 ohm through termination right at the scope. A real simple solution would be to use a BNC T with the center loaded with a 49.9 ohm resistor. Or just look for a 50 ohm through termination on ebay.
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Regards ----- Original Message -----
From: "lop pol via Groups.Io" <the_infinite_penguin@...> To: <[email protected]> Sent: Sunday, June 17, 2018 9:47 PM Subject: [TekScopes] 465 bad rise time Hey guys. I have done a lot of work to this 465. I had initially planned on selling it to help me buy some plugins for my 7633. I decided I don't want to sell it and am keeping it. Today I checked its rise time with a pg506 fast rise. Both channel 1 and 2 closely resemble each other and they are not close to right. Before I start trying to calibrate this thing, does it look like there is some type of component issue left to fix? I am thinking since both channels are so alike there is something wrong besides just out of calibration. Thanks guys. here are some pictures /g/TekScopes/photo/59361/0?p=Name,,,20,1,0,0 /g/TekScopes/photo/59361/1?p=Name,,,20,1,0,0 |
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Re: 465 bad rise time
On Sun, Jun 17, 2018 at 07:03 pm, Harvey White wrote:
In the manual it says to set .05us and remove and add attenuators to keep the 5 divisions and to check for 3.5ns rise time. I used a 50ohm through termination with .2V/div. with the pg506 all most maxed out. I did set 10x mag because I dont know how to see 3.5ns while setting the time at .05us/50ns the trace is wider than 3.5ns. Duplicating the exact setup on my 468 shows the correct 3.5ns rise time without that giant round shoulder. Thanks for your help :) |
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Re: Up to date capacitor list for Tek 2465A and 2465B scopes (2018)- SMPS caps.
Regarding ripple current specifications, I have designed a high ripple application, indeed it is akin to KHz frequency spot welding given the currents pulsing to 800A or so. I have found that the Illinois Capacitor PJ series do handle the duty which runs them at up to 60 C continuous (25C ambient). They do better than Rubycon etc.
They are in parallel banks of 3 @ 2200uF with solder braid augmented PCB traces spec'd to sub 2 m¦¸ per trace. I pre-qualify the capacitors with an ESR meter to sub milliohm? grading and binning for bank balancing. As I look at the data sheet again, I note they are specified for SMPS duty. These capacitors are hammered continuously for 100s of hours per month. I have not had one fail, except when I put in one backward which then pops it in about 30 seconds. Here is an O'scope 'blue' trace of a pulse event using a 50 ¦¸ impedance @ 40A/V? Ion Physics (purpose built) current transformer monitor: I have systems running in Africa where the ambient temperature in the shade is 45C. Ancel |
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Re: 465 bad rise time
On Sun, 17 Jun 2018 18:47:37 -0700, you wrote:
Hey guys. I have done a lot of work to this 465. I had initially planned on selling it to help me buy some plugins for my 7633. I decided I don't want to sell it and am keeping it. Today I checked its rise time with a pg506 fast rise. Both channel 1 and 2 closely resemble each other and they are not close to right. Before I start trying to calibrate this thing, does it look like there is some type of component issue left to fix? I am thinking since both channels are so alike there is something wrong besides just out of calibration. Thanks guys.This may not be exactly what you think. Rise time is measured from 10% to 90%. I'd have to look at the manual for that scope, but I remember that the dotted lines on the graticule are supposed to measure the 10% to 90% parts of the waveform. I think one problem is that you have too little vertical gain at the moment. Bear in mind that the risetime also varies with the vertical gain control. I'd check the manual and see exactly how you are supposed to measure risetime before thinking that the risetime is bad. Harvey
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Re: Up to date capacitor list for Tek 2465A and 2465B scopes (2018)
One of them, Mouser or Digikey, will ship for free or at a reduced rate if you place your order by mail with a check. This is useful if one needs a small number of parts.
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DaveD Sent from a small flat thingy On Jun 17, 2018, at 16:34, Harvey White <madyn@...> wrote:On Sun, 17 Jun 2018 17:04:07 -0400, you wrote:To avoid blanket statements: I've found that some Mouser prices areOn 2018-06-17 2:21 PM, machineguy59 via Groups.Io wrote:About Digikey (Canada). They are FAST: Once I had parts in hand about 12 |
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465 bad rise time
Hey guys. I have done a lot of work to this 465. I had initially planned on selling it to help me buy some plugins for my 7633. I decided I don't want to sell it and am keeping it. Today I checked its rise time with a pg506 fast rise. Both channel 1 and 2 closely resemble each other and they are not close to right. Before I start trying to calibrate this thing, does it look like there is some type of component issue left to fix? I am thinking since both channels are so alike there is something wrong besides just out of calibration. Thanks guys.
here are some pictures /g/TekScopes/photo/59361/0?p=Name,,,20,1,0,0 /g/TekScopes/photo/59361/1?p=Name,,,20,1,0,0 |
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Self Governance of TekScopes.
Members of Tekscopes,
The TekScopes Group Description on our home page says: "All about classic Tektronix test equipment, its use, repair, and collecting." I hope everyone understands I do not have the time to read every post to TekScopes. So I am unaware of the majority of the content posted to TekScopes. On occasion, the content strays beyond our Group Description. I have always been impressed that eventually someone will suggest that the conversation is not consistent with our group description. This is an important stabilizing force that keeps TekScopes relevant. When this happens it would be a big help to me and the other members if one of our "TekScopes Elders" (you know who you are) intervenes as soon as they see this occur and suggests to the offending member that their current conversation is more appropriate elsewhere. In the spirit of "See Something, Say Something", I would appreciate the TekScopes Elders making it their responsibly to gently guide any stray conversation back to Tektronix. I hope it will only take one reminder from a TekScopes Elder to bring the stray conversation back to Tektronix. If that doesn't happen then please send me an email so I can intervene and stop it. Thank you in advance, Dennis Tillman W7PF PS: I would greatly appreciate it if we could keep any follow-up comments to an absolute minimum so first take a look at these three categories to determine your next move: 1) If you understand what I am proposing and you are one of the TekScopes Elders then there is no need to tell me. Please start now to "See Something, Say Something". 2) If you are someone who feels the need to say you approve of what I proposed above please refrain from posting at all. 3) If you disagree with what I am proposing pleasing contact me directly OFF LINE at dennis@... <mailto:dennis@...> and explain how I can do this better. |
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Re: Up to date capacitor list for Tek 2465A and 2465B scopes (2018)
On Sun, 17 Jun 2018 17:04:07 -0400, you wrote:
On 2018-06-17 2:21 PM, machineguy59 via Groups.Io wrote:To avoid blanket statements: I've found that some Mouser prices are...About Digikey (Canada). They are FAST: Once I had parts in hand about 12 cheaper than Digikey prices. I've also found that Mouser does not carry some parts that I need (they went Altera rather than Xilinx, and apparently carry NO Xilinx parts. Didn't check Digikey for Altera). I'm in the southeast, so Mouser is closer for me and a bit faster. As in any buy, consider how many you need and what the economies of a bulk buy happen to be. SMT resistor may be 15 cents in unit quantities, in lots of 100, you may be paying 0.5 cents. Once you start ordering that kind of stuff, as long as you don't order too many, the shipping is the killer. You tend to want to spend enough that the shipping is not more than the parts total. Harvey
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Re: Up to date capacitor list for Tek 2465A and 2465B scopes (2018)
On 2018-06-17 2:21 PM, machineguy59 via Groups.Io wrote:
...About Digikey (Canada). They are FAST: Once I had parts in hand about 12 hours after ordering on the web. Next day is usual. For me they also have much cheaper shipping than Mouser. --Toby |
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Re: Up to date capacitor list for Tek 2465A and 2465B scopes (2018)
Menahem, You may address me as Ron, or Mac (for machineguy).? I usually use Mac on the net and Ron in the "real world".? As a brief introduction, I am 78 years old, retired electronics engineer, now hobbyist, living in Iowa, USA.? Its hot here too (94 degrees F on many days), but air conditioning keeps it at a nice 73 degrees.? I got into repairing Tek scopes because they were everywhere during my working years but unaffordable.? I read the report on your 2465B scope restoration and decided I could do that too.? I now have six 24x5 scopes sitting in my lab, three work, one is being "built" and two are donors.? My wife wants me to "thin the herd" but we have an agreement: She wont throw out my scopes and I wont throw out her dishwasher.? My technical abilities are competent but not expert, too many years in management.? My repair objectives are equal or better than OEM (which in the case of Tek equipment is world class performance).? My three fully working scopes seem to achieve that goal.
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Honestly, I was surprised and a bit offended when you first deprecated my updated list.? I had posted it to help someone who was creating a new list "from scratch".? He had asked for help and received little response.? So I offered the list I use.? I was embarrassed that it had two errors but I do think it helped him.? You might do better for him and I encourage you to post a list.? But this one is the best I have.? I use it and it works. I agree with you, Nichicon is a better choice than Panasonic.? This is evident in their specifications.? Panasonic lists an ESR that is 30% or more worse in ESR than Nichicon.? This may account for the difference you measured in ripple reduction between the two.? (BTW, you may want to check your photos in the file section.? There are only two photos, not four and I believe the key photos are missing.)? But I used Panasonic in six locations.? Based on my agreement with your advice, I have changed my list to use the Nichicon equivalent in these locations.? For what its worth, I have preferred Nichicon to Panasonic for some time, just had not updated my list. Like you, I give little weight to forecast life expectancy over 5000 hours.? But if all important parameters are equal, I use life expectancy as a factor. Also like you, I used to avoid "over voltage" specifications in electrolytic capacitors.? But my research showed that higher voltage rated caps often had lower ESR and manufacturers often suggested de-rating their caps in hard stress applications by as much as 50%.? I reasoned then that if it was good for high stress applications, it was acceptable for moderate stress applications.? This discussion and my recent research has given me confidence in that decision. Finally, I use Digikey for parts.? I have no disdain for Mouser but Digikey is more convenient to me.? They are less than 200 miles from my home, shipping is fast (typically two days from order to arrival here), and cheap (as low as 3.95 US for a complete set of caps).? So my list does not include Mouser part numbers. ? Again, thank you for your explanations.? I hope mine are useful to you. Ron On ?Sunday?, ?June? ?17?, ?2018? ?02?:?46?:?49? ?AM? ?CDT, M Yachad <yachadm@...> wrote:
MachineGuy (I¡¯d really like to address you by your real name!) Thanks for that info from the tin-man. I can certainly relate to the manufacturer¡¯s published data. I will take this into consideration the next time I have to select caps. To address certain points: 1.??? I am not at all biased against Panasonic caps. They are superb, and I use the EB in Linear audio applications all the time. They are my go-to for that specific application. 2.??? I also use the Panasonic TSHA and ED/EE Snap-ins as my go-to PSU filter capacitors, with Nichicon GU as my second choice. 3.??? So, the question arises, WHY do I NOT recommend the EB in THIS Tek PSU application? 4.??? It is important to understand the function of a cap in each particular place in the circuit. In any PSU application, the AC ripple BETWEEN the Bridge rectifier and the Regulators is enormous. AFTER the regulators, the AC ripple is negligible. 5.??? A few years ago, to quieten my curiosity, I did a test on an older amplifier using 4 new apparently identical 4700uF 25V and 50V capacitors mounted BETWEEN the Bridge and the bank of Regulators (some 78xx, 79xx, 317, 319). The Nichicon HE caps reduced the residual AC ripple to approx 1V p-p (with no discernible difference between the 25V and 50V cap). The other caps reduced the residual ripple to 2V p-p. See attached pictures. This is a test which any of you can easily do, any time. /g/TekScopes/album?id=59343 6.??? That proved to me that the HE has a significant advantage in reducing AC ripple, over another respected brand-name cap. On the datasheets, all the numbers pretty much matched up, but in the real world of flowing voltage and current, my scope waveform showed a substantially significant advantage to the HE. 7.??? However, AFTER the regulators, where ripple is negligible, an EB is an excellent choice. The superior capability of the HE regarding ripple damping is of no advantage here. On this Tek PSU, has anyone actually done any research to specify each cap¡¯s function? From the postings here, I don¡¯t think so. I haven¡¯t. So, unless someone is willing to go and locate each cap on the circuit, and determine whether it is in a low-ripple part of the circuit (where an EB would be acceptable), or it is in a high-ripple part,? I think that we need to globally specify HE or PW (functionally equivalent), in order to be on the safe side for ALL applications. That¡¯s what I did, with full confidence that my choice would give me the lowest ACTUAL ripple on all circuits. If a user installs EB in a high-ripple area BEFORE the regulators, will the machine work? Of course it will. But will it work as well, if an HE or PW is installed? My test states not. After all, a SMPS with loads of AC ripple in all parts of the circuit, is NOT like a linear PSU, at all. It¡¯s the difference in being able to tune a high-performance engine, to get the last ounce of available HP out of it. The posters who are asking these questions are people who do NOT have any substantial electronics background, theory or practice. I think it is incumbent on us (the techs with long experience) to point them in a direction which will give them an optimal and safe solution, so that they don¡¯t have to tear their hair out, buying parts which don¡¯t fit, or worrying whether what they choose will last or not. Regarding the Lifetime numbers of the data provided by MachineGuy: A 5000Hr lifetime is provided for a (boiling) CONSTANT temperature of 105¡ãC. If the caps in my Tek scope are reaching that temperature, then my scope is on the way to the garbage dump, very quickly, and the 5000hr lifetime is functionally irrelevant. I have measured the temperature of my HE caps in my A2A1/A3 PSU block, and the hottest individual cap temperature which I measured was 38¡ãC. The average temp of the caps was room temperature. And it IS hot here in Israel ¨C I¡¯m not just talking about the fires from the Gazan terrorists. ¡°For every 10 degree Centigrade decrease in operating temperature, the capacitor life is extended by a factor of two.¡± So, if my HE caps are running at a constant 40¡ãC, then their expected lifetime is 5000 x 2 to the power of 6 (=64, check my math) = 320,000 hrs = more than 36 years; scope on all the time, never being switched off. Given that the data supplied above stated that cap¡¯s casing would breakdown after about 15 years, then there is no apparent benefit HERE of choosing a 10000 hr cap over a 5000 hr, except for the status. So, IMO what we should be concerned about, is WHAT does the waveform look like at all the HIGH-RIPPLE positions in this Tek SMPS PSU circuit, and then select the cap which dampens that ripple most effectively. To my experience, the Nichicon HE fits the bill most effectively. Menahem |
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Re: Up to date capacitor list for Tek 2465A and 2465B scopes (2018)
Chuck Harris
Then you should have seen it in my last post, but here
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it is again: ------------------------------------------------------ Ok, we are all engineers here, so, we know that ripple voltage is pretty directly related to frequency, current, and capacitance by the equation: i(t) = -CdV/dt [We can drop the "-" sign if we remember to get our dV in the right direction so that we don't get a negative capacitance.] Looking at the oscilloscope traces, we see that in: case 1) C = ?, dV = 2V, and dt = 5ms, and in case 2) C = 4700uF, dV = 1.2V, and dt = 5ms. Solving for i, we get 1.13A Rearranging the equation and substituting the mystery cap's ripple voltage: C = idt/dV = 1.13A x 5ms/2V = 2820uF Hold the phone there Menahem! If that really is a 4700uf Brand X cap, it is either short 2000uf, or has about an ohm of ESR... [EIA guidlines show a 4700uf, 25V, has to be less than 0.099 ohm ESR, and a 4700uf, 50V, has to be less than 0.071 ohm ESR.] So, which is it: A 2800uf capacitor marked as 4700uf? A less than 0.1 ohm ESR cap with 1 ohm ESR? A fib about the capacitance value? -------------------------------------------------------- Do you have an answer? -Chuck Harris M Yachad wrote: Talk, I'm listening. |
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Re: Up to date capacitor list for Tek 2465A and 2465B scopes (2018)
Chuck Harris
Well, consider me chastised.
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I'm guessing that you and I have a different idea of what constitutes an attack. The math is simple, tried and true, and leads to the inescapable conclusion that if everything is as you said, the capacitor you are comparing to the HE can't be 4700uf. Let's talk about that. -Chuck Harris M Yachad wrote: Chuck |
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Re: Up to date capacitor list for Tek 2465A and 2465B scopes (2018)
Chuck Harris
So, let see if I got this straight:
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You did a comparison between brand X and Nichicon HE caps, and you found that the Nichicon HE outperformed the brand X capacitor 2 to 1. Even gave us some pretty pictures. Ok, wait, there is some fine print: The brand X cap is old, and apparently to avoid embarrassing the manufacturer, you won't tell their name. [Wait! 3:40AM, and the text just changed! Now the other cap is 4700uf 25V and 50V, not just an old cap... I hate it when that happens...] Ok, we are all engineers here, so, we know that ripple voltage is pretty directly related to frequency, current, and capacitance by the equation: i(t) = -CdV/dt [We can drop the "-" sign if we remember to get our dV in the right direction so that we don't get a negative capacitance.] Looking at the oscilloscope traces, we see that in: case 1) C = ?, dV = 2V, and dt = 5ms, and in case 2) C = 4700uF, dV = 1.2V, and dt = 5ms. Solving for i, we get 1.13A Rearranging the equation and substituting the mystery cap's ripple voltage: C = idt/dV = 1.13 x 5ms/2V = 2820uF Hold the phone there Menahem! If that really is a 4700uf Brand X cap, it is either short 2000uf, or has about an ohm of ESR... [EIA guidlines show a 4700uf 25V has to be less than 0.099 ohm ESR, and a 4700uf 50V has to be less than 0.071 ohm ESR.] So, which is it: A 2800uf capacitor marked as 4700uf? A less than 0.1 ohm ESR cap with 1 ohm ESR? A fib about the capacitance value? You state that any of us can do the same test at anytime... How is that so? You didn't tell us anything about the brand X capacitor we are testing against... So, I guess absent any information we have to take your word. Absent more information, I probably won't. -Chuck Harris M Yachad wrote: MachineGuy |
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Re: Up to date capacitor list for Tek 2465A and 2465B scopes (2018)
MachineGuy
(I¡¯d really like to address you by your real name!) Thanks for that info from the tin-man. I can certainly relate to the manufacturer¡¯s published data. I will take this into consideration the next time I have to select caps. To address certain points: 1. I am not at all biased against Panasonic caps. They are superb, and I use the EB in Linear audio applications all the time. They are my go-to for that specific application. 2. I also use the Panasonic TSHA and ED/EE Snap-ins as my go-to PSU filter capacitors, with Nichicon GU as my second choice. 3. So, the question arises, WHY do I NOT recommend the EB in THIS Tek PSU application? 4. It is important to understand the function of a cap in each particular place in the circuit. In any PSU application, the AC ripple BETWEEN the Bridge rectifier and the Regulators is enormous. AFTER the regulators, the AC ripple is negligible. 5. A few years ago, to quieten my curiosity, I did a test on an older amplifier using 4 new apparently identical 4700uF 25V and 50V capacitors mounted BETWEEN the Bridge and the bank of Regulators (some 78xx, 79xx, 317, 319). The Nichicon HE caps reduced the residual AC ripple to approx 1V p-p (with no discernible difference between the 25V and 50V cap). The other caps reduced the residual ripple to 2V p-p. See attached pictures. This is a test which any of you can easily do, any time. /g/TekScopes/album?id=59343 6. That proved to me that the HE has a significant advantage in reducing AC ripple, over another respected brand-name cap. On the datasheets, all the numbers pretty much matched up, but in the real world of flowing voltage and current, my scope waveform showed a substantially significant advantage to the HE. 7. However, AFTER the regulators, where ripple is negligible, an EB is an excellent choice. The superior capability of the HE regarding ripple damping is of no advantage here. On this Tek PSU, has anyone actually done any research to specify each cap¡¯s function? From the postings here, I don¡¯t think so. I haven¡¯t. So, unless someone is willing to go and locate each cap on the circuit, and determine whether it is in a low-ripple part of the circuit (where an EB would be acceptable), or it is in a high-ripple part, I think that we need to globally specify HE or PW (functionally equivalent), in order to be on the safe side for ALL applications. That¡¯s what I did, with full confidence that my choice would give me the lowest ACTUAL ripple on all circuits. If a user installs EB in a high-ripple area BEFORE the regulators, will the machine work? Of course it will. But will it work as well, if an HE or PW is installed? My test states not. After all, a SMPS with loads of AC ripple in all parts of the circuit, is NOT like a linear PSU, at all. It¡¯s the difference in being able to tune a high-performance engine, to get the last ounce of available HP out of it. The posters who are asking these questions are people who do NOT have any substantial electronics background, theory or practice. I think it is incumbent on us (the techs with long experience) to point them in a direction which will give them an optimal and safe solution, so that they don¡¯t have to tear their hair out, buying parts which don¡¯t fit, or worrying whether what they choose will last or not. Regarding the Lifetime numbers of the data provided by MachineGuy: A 5000Hr lifetime is provided for a (boiling) CONSTANT temperature of 105¡ãC. If the caps in my Tek scope are reaching that temperature, then my scope is on the way to the garbage dump, very quickly, and the 5000hr lifetime is functionally irrelevant. I have measured the temperature of my HE caps in my A2A1/A3 PSU block, and the hottest individual cap temperature which I measured was 38¡ãC. The average temp of the caps was room temperature. And it IS hot here in Israel ¨C I¡¯m not just talking about the fires from the Gazan terrorists. ¡°For every 10 degree Centigrade decrease in operating temperature, the capacitor life is extended by a factor of two.¡± So, if my HE caps are running at a constant 40¡ãC, then their expected lifetime is 5000 x 2 to the power of 6 (=64, check my math) = 320,000 hrs = more than 36 years; scope on all the time, never being switched off. Given that the data supplied above stated that cap¡¯s casing would breakdown after about 15 years, then there is no apparent benefit HERE of choosing a 10000 hr cap over a 5000 hr, except for the status. So, IMO what we should be concerned about, is WHAT does the waveform look like at all the HIGH-RIPPLE positions in this Tek SMPS PSU circuit, and then select the cap which dampens that ripple most effectively. To my experience, the Nichicon HE fits the bill most effectively. Menahem |
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Re: Tek 2337 (looks mint) on Goodwill.
Same form factor as the 2335 and 2336; each one has a different feature in
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integrated lid. The 2336 has an LCD readout of the intensified sweep time. My first scope was a 2336; still have it as my go-to portable. Dave Casey On Sat, Jun 16, 2018, 11:10 AM Artekmedia <manuals@...> wrote:
Looks like it is very clean, If I still lived in Ft worth I'd run over |
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Re: My 422
Ohio. here I thought you were east coast somewhere...no problem on the meters ...once in awhile things fall into place...like the item etc is down the street (from me), literally, I walked down and shipped it out for a fella!
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I am in the north bay/ napa area but travel all over the place for my jobs ( music performance) and I never know if and when till hired....geez that reminds me I have reeds to make too......summer is my busy time although it seems to run in spurts. i will post both collector and base. I do want to match the xstrs better. so I do need to go back in. my pwr supply is pretty much limited to 25V at 4A absolute max before it sags. and I will post what I did to open the loop and test. next is my just acquired 475 that needs attention ( I am borrowing one). this one has options 4 (RFI) and 7 (AC/DC). also has a mod 93 what ever that happens to be. I will have to ask the group.....someone will know. Problem is using the Cal signal ( only test i ran when I purchased. ) collapses as it is moved vertically up or down to go off the screen...like it hits a wall and collapses into it at the top and bottom of the screen. at least it has a trace and controls work.....I am hoping just a pwr supply issue. may be vertical amps, or dirty sockets....do not know...I have not opened the case. currently I am in the SF bay area, back to moms in the hills ( Railroad Flat...East of Stockton)..I dislike having to be in two places!? that is also why info is not so fast while working on something and sometimes stuff get left in one place or the other and things wait for a week or more.....I am care taker for mom...84 going on 300..... nuff on this Your assistance has been greatly appreciated. ¸é±ð²Ô¨¦±ð On 2018-06-16 04:52 PM, Jeff Urban wrote:
Ohio here. Not exactly a stone's throw. If I could get there it would be with my friend the truck driver who goes that way alot, but I either couldn't stay more than a few minutes or need another way home. Driving it is out of the question for me. |
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